In telephone systems having metallic crosspoints in its switching network, control and supervisory signals are developed in circuits associated with the junctor or supervisory side of the network. A considerable savings in access control devices and source circuits is effected in this manner.
In telephone systems which do not have a direct metallic path from the line side of the switching network to the supervisory side, a problem of economics in equipment arises in transmitting high voltage signals and service signals to lines. The same problem arises both in space division systems using semi-conductive crosspoints and in time division systems employing pulse modulation switching. The high voltage and service signals such as supervisory signals cannot be sent through the switching network. Therefore, these signals must be originated on the line side. Equipment must be provided to couple the sources of these signals to the lines on demand. This equipment comprises extensive amounts of adapters and auxiliary networks. In order to apply the signals to the line side, the usual approach is to provide adapting equipment on a per-line basis for connection of a necessary source circuit.